This application is based on Korean Patent Application No. 2002-12975 filed on Mar. 11, 2002, the disclosure of which is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates in general to a rendering system, and more particularly, to a rendering system and method for producing a realistic two-dimensional (2D) computer graphic (CG) image, which uses three-dimensional (3D) geometry data produced by a commercial 3D computer-aided design (CAD) system, and a recording medium for the same.
2. Description of the Related Art
Recently, CAD systems, and particularly 3D CAD systems, are widely used to design products. CAD systems include a CAD software, which is driven on a computer for-CAD operations, and programs and resources, which are related to the driving of the CAD software. Rendering systems include a rendering software, which is driven on a computer for rendering operations, and programs and resources, which are related to the rendering software.
When products to be mass-produced are designed using a CAD system, a realistic graphic image is required to verify and evaluate the design.
In order to effectively visualize a 3D model using a CAD system, it is necessary to exactly and realistically present the geometry and material of the products. This operation is referred to as a rendering.
When a CAD system does not include a rendering function or when a rendering function included in a CAD system is inadequate to produce an image having satisfactory quality desired by a user, an external CG rendering system providing a high-level rendering function is used to produce a CG rendering image for a 3D model.
In order to generate a high-level rendering image, using 3D CAD data that is modeled in a commercial 3D CAD system, and using an independent CG rendering system, the following processes are performed.
After storing 3D geometry data, i.e., 3D CAD data that has been completely modeled in a 3D CAD system, the geometry data is stored as an external file using a standard 3D CAD file storage function, i.e., a file export function, provided by a commercial 3D CAD software. Here, the stored standard 3D CAD file is an Initial Graphics Exchange Specification (IGES) file, the Standard for the Exchange of Product (STEP) Model Data file, or a standard 3D data file corresponding thereto. FIG. 9 shows the structure of an IGES file. Referring to FIG. 9, the IGES file just contains information on pieces of surface geometry data that are linearly arranged, but the IGES file does not contain information on a hierarchy structure in the geometries.
Next, the standard 3D data file is stored in a database (DB) of the CG rendering software using a data input function, i.e., a file import function, of the CG rendering software. Here, the data on the geometry hierarchy structure cannot be maintained, and some geometries may be changed. Thus, after the storing is completed, the geometry hierarchy structure data that has been lost during conversion into the standard 3D data file and the geometry data that has been transformed, due to the use of different systems, are corrected and restored.
After the geometry data and the geometry hierarchy structure data are completely corrected, scenes are edited for rendering. After the editing is completed, a high-level rendering process is performed to produce a final image. Ray tracing or A-Buffering is usually used for the high-level rendering.
In a conventional rendering system and method, an IGES file, i.e., a standard 3D data file that is used for data transmission between commercial CAD software and CG rendering software, does not include geometry hierarchy structure data, and errors may occur in geometry data during conversion into the standard 3D data file.
The geometry hierarchy structure data is necessary in order to edit scenes based on color/material in units of parts and to perform texture mapping, during scene editing for rendering using 3D CG rendering software. In addition, when the standard 3D data file is read into the CG rendering software, the CG rendering software needs to restore the lost geometry hierarchy structure data by creating an internal data structure that maintains the geometry hierarchy structure data and to provide a user interface allowing generation/editing of the internal data structure.
In addition, when errors occur in the geometry data, a user needs to correct the errors in the geometry data using a high-level 3D modeling function provided by the CG rendering software. In order to restore lost data, a user needs to correct the data defining the geometries and the hierarchy structure of the geometries in the CG rendering software. Here, the user's operation may take several hours through several days depending on the content of the modeling, the amount of lost data, and the performance of the correction function.
Additionally, the user may need to make a modification to the geometries after completion of scene editing for rendering. During the designing of a product to be mass-produced, the modification to the geometry of the product is usually performed in a 3D CAD system. The geometry modified in the 3D CAD system must be used in a rendering operation of a rendering system. Generally, when a commercial CG rendering software is used, the modified CAD geometry data is stored in a standard file format, and then read by the rendering system. Here, existing data about material, for example, is not preserved, and thus the previously designed data about material must be re-edited.
In addition, a light and a camera need to be appropriately setup for a rendering operation. This type of setup requires expert skills. However, in conventional rendering methods, a new setup is performed whenever a rendering operation is performed. Consequently, techniques are not shared, thereby increasing the operating time.